Code-Division Multiple Access (CDMA) has become one of the most prominent schemes for wireless communication systems. In a given radio frequency channel, individual CDMA data channels are distinguished from one another by different code sequences. A multiple code (MC) CDMA receiver allows for communication at J&gt;1 times the base data rate by simultaneously demodulating J data channels. Due to the wide band nature of the CDMA signal, the receivers can be made robust against fading by exploiting the multipath diversity using a RAKE receiver. In a coherent CDMA system, a pilot signal is often transmitted so that the RAKE receiver can obtain amplitude and phase estimates of the channel needed for coherent detection. This pilot signal is usually designed to be orthogonal to the data channel spreading codes so that in the rare case of no multipath dispersion, the pilot signal will not cause interference at the matched filter output of the desired data channel. If there is multipath dispersion, there will be unwanted interference at the RAKE receiver's matched filter output due to a variety of multipath components. Specifically, for a given multipath component of a desired data channel at the receiver, its RAKE receiver output will have unwanted contributions due to other multipath components of itself, the other channels, and the pilot signal. As a result, the performances of the conventional RAKE and MC-CDMA receiver suffer as a consequence of ignoring the interchannel multipath interference .
In our recently allowed patent application entitled PILOT INTERFERENCE CANCELLATION FOR A COHERENT WIRELESS CODE DIVISION MULTIPLE ACCESS RECEIVER, Ser. No. 08/700,266, filed on Aug. 20, 1997, we introduced a pilot interference canceller which improved the performance of a coherent CDMA receiver by reconstructing and canceling out pilot multipath interference prior to demodulation by the RAKE receiver. Notwithstanding the interference reduction provided by the pilot interference canceller, there is a continuing need to eliminate the interchannel multipath components of interference in MC-CDMA receivers.